kernel/cred.c

   1 /* Task credentials management - see Documentation/credentials.txt
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells ([email protected])
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/cred.h>
  13 #include <linux/slab.h>
  14 #include <linux/sched.h>
  15 #include <linux/key.h>
  16 #include <linux/keyctl.h>
  17 #include <linux/init_task.h>
  18 #include <linux/security.h>
  19 #include <linux/cn_proc.h>
  20 #include "cred-internals.h"
  21
  22 #if 0
  23 #define kdebug(FMT, ...) \
  24         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  25 #else
  26 static inline __attribute__((format(printf, 1, 2)))
  27 void no_printk(const char *fmt, ...)
  28 {
  29 }
  30 #define kdebug(FMT, ...) \
  31         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  32 #endif
  33
  34 static struct kmem_cache *cred_jar;
  35
  36 /*
  37  * The common credentials for the initial task's thread group
  38  */
  39 #ifdef CONFIG_KEYS
  40 static struct thread_group_cred init_tgcred = {
  41         .usage  = ATOMIC_INIT(2),
  42         .tgid   = 0,
  43         .lock   = SPIN_LOCK_UNLOCKED,
  44 };
  45 #endif
  46
  47 /*
  48  * The initial credentials for the initial task
  49  */
  50 struct cred init_cred = {
  51         .usage                  = ATOMIC_INIT(4),
  52 #ifdef CONFIG_DEBUG_CREDENTIALS
  53         .subscribers            = ATOMIC_INIT(2),
  54         .magic                  = CRED_MAGIC,
  55 #endif
  56         .securebits             = SECUREBITS_DEFAULT,
  57         .cap_inheritable        = CAP_INIT_INH_SET,
  58         .cap_permitted          = CAP_FULL_SET,
  59         .cap_effective          = CAP_INIT_EFF_SET,
  60         .cap_bset               = CAP_INIT_BSET,
  61         .user                   = INIT_USER,
  62         .group_info             = &init_groups,
  63 #ifdef CONFIG_KEYS
  64         .tgcred                 = &init_tgcred,
  65 #endif
  66 };
  67
  68 static inline void set_cred_subscribers(struct cred *cred, int n)
  69 {
  70 #ifdef CONFIG_DEBUG_CREDENTIALS
  71         atomic_set(&cred->subscribers, n);
  72 #endif
  73 }
  74
  75 static inline int read_cred_subscribers(const struct cred *cred)
  76 {
  77 #ifdef CONFIG_DEBUG_CREDENTIALS
  78         return atomic_read(&cred->subscribers);
  79 #else
  80         return 0;
  81 #endif
  82 }
  83
  84 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  85 {
  86 #ifdef CONFIG_DEBUG_CREDENTIALS
  87         struct cred *cred = (struct cred *) _cred;
  88
  89         atomic_add(n, &cred->subscribers);
  90 #endif
  91 }
  92
  93 /*
  94  * Dispose of the shared task group credentials
  95  */
  96 #ifdef CONFIG_KEYS
  97 static void release_tgcred_rcu(struct rcu_head *rcu)
  98 {
  99         struct thread_group_cred *tgcred =
 100                 container_of(rcu, struct thread_group_cred, rcu);
 101
 102         BUG_ON(atomic_read(&tgcred->usage) != 0);
 103
 104         key_put(tgcred->session_keyring);
 105         key_put(tgcred->process_keyring);
 106         kfree(tgcred);
 107 }
 108 #endif
 109
 110 /*
 111  * Release a set of thread group credentials.
 112  */
 113 static void release_tgcred(struct cred *cred)
 114 {
 115 #ifdef CONFIG_KEYS
 116         struct thread_group_cred *tgcred = cred->tgcred;
 117
 118         if (atomic_dec_and_test(&tgcred->usage))
 119                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
 120 #endif
 121 }
 122
 123 /*
 124  * The RCU callback to actually dispose of a set of credentials
 125  */
 126 static void put_cred_rcu(struct rcu_head *rcu)
 127 {
 128         struct cred *cred = container_of(rcu, struct cred, rcu);
 129
 130         kdebug("put_cred_rcu(%p)", cred);
 131
 132 #ifdef CONFIG_DEBUG_CREDENTIALS
 133         if (cred->magic != CRED_MAGIC_DEAD ||
 134             atomic_read(&cred->usage) != 0 ||
 135             read_cred_subscribers(cred) != 0)
 136                 panic("CRED: put_cred_rcu() sees %p with"
 137                       " mag %x, put %p, usage %d, subscr %d\n",
 138                       cred, cred->magic, cred->put_addr,
 139                       atomic_read(&cred->usage),
 140                       read_cred_subscribers(cred));
 141 #else
 142         if (atomic_read(&cred->usage) != 0)
 143                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 144                       cred, atomic_read(&cred->usage));
 145 #endif
 146
 147         security_cred_free(cred);
 148         key_put(cred->thread_keyring);
 149         key_put(cred->request_key_auth);
 150         release_tgcred(cred);
 151         if (cred->group_info)
 152                 put_group_info(cred->group_info);
 153         free_uid(cred->user);
 154         kmem_cache_free(cred_jar, cred);
 155 }
 156
 157 /**
 158  * __put_cred - Destroy a set of credentials
 159  * @cred: The record to release
 160  *
 161  * Destroy a set of credentials on which no references remain.
 162  */
 163 void __put_cred(struct cred *cred)
 164 {
 165         kdebug("__put_cred(%p{%d,%d})", cred,
 166                atomic_read(&cred->usage),
 167                read_cred_subscribers(cred));
 168
 169         BUG_ON(atomic_read(&cred->usage) != 0);
 170 #ifdef CONFIG_DEBUG_CREDENTIALS
 171         BUG_ON(read_cred_subscribers(cred) != 0);
 172         cred->magic = CRED_MAGIC_DEAD;
 173         cred->put_addr = __builtin_return_address(0);
 174 #endif
 175         BUG_ON(cred == current->cred);
 176         BUG_ON(cred == current->real_cred);
 177
 178         call_rcu(&cred->rcu, put_cred_rcu);
 179 }
 180 EXPORT_SYMBOL(__put_cred);
 181
 182 /*
 183  * Clean up a task's credentials when it exits
 184  */
 185 void exit_creds(struct task_struct *tsk)
 186 {
 187         struct cred *cred;
 188
 189         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 190                atomic_read(&tsk->cred->usage),
 191                read_cred_subscribers(tsk->cred));
 192
 193         cred = (struct cred *) tsk->real_cred;
 194         tsk->real_cred = NULL;
 195         validate_creds(cred);
 196         alter_cred_subscribers(cred, -1);
 197         put_cred(cred);
 198
 199         cred = (struct cred *) tsk->cred;
 200         tsk->cred = NULL;
 201         validate_creds(cred);
 202         alter_cred_subscribers(cred, -1);
 203         put_cred(cred);
 204
 205         cred = (struct cred *) tsk->replacement_session_keyring;
 206         if (cred) {
 207                 tsk->replacement_session_keyring = NULL;
 208                 validate_creds(cred);
 209                 put_cred(cred);
 210         }
 211 }
 212
 213 /*
 214  * Allocate blank credentials, such that the credentials can be filled in at a
 215  * later date without risk of ENOMEM.
 216  */
 217 struct cred *cred_alloc_blank(void)
 218 {
 219         struct cred *new;
 220
 221         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 222         if (!new)
 223                 return NULL;
 224
 225 #ifdef CONFIG_KEYS
 226         new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 227         if (!new->tgcred) {
 228                 kmem_cache_free(cred_jar, new);
 229                 return NULL;
 230         }
 231         atomic_set(&new->tgcred->usage, 1);
 232 #endif
 233
 234         atomic_set(&new->usage, 1);
 235
 236         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 237                 goto error;
 238
 239 #ifdef CONFIG_DEBUG_CREDENTIALS
 240         new->magic = CRED_MAGIC;
 241 #endif
 242         return new;
 243
 244 error:
 245         abort_creds(new);
 246         return NULL;
 247 }
 248
 249 /**
 250  * prepare_creds - Prepare a new set of credentials for modification
 251  *
 252  * Prepare a new set of task credentials for modification.  A task's creds
 253  * shouldn't generally be modified directly, therefore this function is used to
 254  * prepare a new copy, which the caller then modifies and then commits by
 255  * calling commit_creds().
 256  *
 257  * Preparation involves making a copy of the objective creds for modification.
 258  *
 259  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 260  *
 261  * Call commit_creds() or abort_creds() to clean up.
 262  */
 263 struct cred *prepare_creds(void)
 264 {
 265         struct task_struct *task = current;
 266         const struct cred *old;
 267         struct cred *new;
 268
 269         validate_process_creds();
 270
 271         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 272         if (!new)
 273                 return NULL;
 274
 275         kdebug("prepare_creds() alloc %p", new);
 276
 277         old = task->cred;
 278         memcpy(new, old, sizeof(struct cred));
 279
 280         atomic_set(&new->usage, 1);
 281         set_cred_subscribers(new, 0);
 282         get_group_info(new->group_info);
 283         get_uid(new->user);
 284
 285 #ifdef CONFIG_KEYS
 286         key_get(new->thread_keyring);
 287         key_get(new->request_key_auth);
 288         atomic_inc(&new->tgcred->usage);
 289 #endif
 290
 291 #ifdef CONFIG_SECURITY
 292         new->security = NULL;
 293 #endif
 294
 295         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 296                 goto error;
 297         validate_creds(new);
 298         return new;
 299
 300 error:
 301         abort_creds(new);
 302         return NULL;
 303 }
 304 EXPORT_SYMBOL(prepare_creds);
 305
 306 /*
 307  * Prepare credentials for current to perform an execve()
 308  * - The caller must hold current->cred_guard_mutex
 309  */
 310 struct cred *prepare_exec_creds(void)
 311 {
 312         struct thread_group_cred *tgcred = NULL;
 313         struct cred *new;
 314
 315 #ifdef CONFIG_KEYS
 316         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 317         if (!tgcred)
 318                 return NULL;
 319 #endif
 320
 321         new = prepare_creds();
 322         if (!new) {
 323                 kfree(tgcred);
 324                 return new;
 325         }
 326
 327 #ifdef CONFIG_KEYS
 328         /* newly exec'd tasks don't get a thread keyring */
 329         key_put(new->thread_keyring);
 330         new->thread_keyring = NULL;
 331
 332         /* create a new per-thread-group creds for all this set of threads to
 333          * share */
 334         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 335
 336         atomic_set(&tgcred->usage, 1);
 337         spin_lock_init(&tgcred->lock);
 338
 339         /* inherit the session keyring; new process keyring */
 340         key_get(tgcred->session_keyring);
 341         tgcred->process_keyring = NULL;
 342
 343         release_tgcred(new);
 344         new->tgcred = tgcred;
 345 #endif
 346
 347         return new;
 348 }
 349
 350 /*
 351  * prepare new credentials for the usermode helper dispatcher
 352  */
 353 struct cred *prepare_usermodehelper_creds(void)
 354 {
 355 #ifdef CONFIG_KEYS
 356         struct thread_group_cred *tgcred = NULL;
 357 #endif
 358         struct cred *new;
 359
 360 #ifdef CONFIG_KEYS
 361         tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
 362         if (!tgcred)
 363                 return NULL;
 364 #endif
 365
 366         new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
 367         if (!new)
 368                 return NULL;
 369
 370         kdebug("prepare_usermodehelper_creds() alloc %p", new);
 371
 372         memcpy(new, &init_cred, sizeof(struct cred));
 373
 374         atomic_set(&new->usage, 1);
 375         set_cred_subscribers(new, 0);
 376         get_group_info(new->group_info);
 377         get_uid(new->user);
 378
 379 #ifdef CONFIG_KEYS
 380         new->thread_keyring = NULL;
 381         new->request_key_auth = NULL;
 382         new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
 383
 384         atomic_set(&tgcred->usage, 1);
 385         spin_lock_init(&tgcred->lock);
 386         new->tgcred = tgcred;
 387 #endif
 388
 389 #ifdef CONFIG_SECURITY
 390         new->security = NULL;
 391 #endif
 392         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
 393                 goto error;
 394         validate_creds(new);
 395
 396         BUG_ON(atomic_read(&new->usage) != 1);
 397         return new;
 398
 399 error:
 400         put_cred(new);
 401         return NULL;
 402 }
 403
 404 /*
 405  * Copy credentials for the new process created by fork()
 406  *
 407  * We share if we can, but under some circumstances we have to generate a new
 408  * set.
 409  *
 410  * The new process gets the current process's subjective credentials as its
 411  * objective and subjective credentials
 412  */
 413 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 414 {
 415 #ifdef CONFIG_KEYS
 416         struct thread_group_cred *tgcred;
 417 #endif
 418         struct cred *new;
 419         int ret;
 420
 421         mutex_init(&p->cred_guard_mutex);
 422
 423         if (
 424 #ifdef CONFIG_KEYS
 425                 !p->cred->thread_keyring &&
 426 #endif
 427                 clone_flags & CLONE_THREAD
 428             ) {
 429                 p->real_cred = get_cred(p->cred);
 430                 get_cred(p->cred);
 431                 alter_cred_subscribers(p->cred, 2);
 432                 kdebug("share_creds(%p{%d,%d})",
 433                        p->cred, atomic_read(&p->cred->usage),
 434                        read_cred_subscribers(p->cred));
 435                 atomic_inc(&p->cred->user->processes);
 436                 return 0;
 437         }
 438
 439         new = prepare_creds();
 440         if (!new)
 441                 return -ENOMEM;
 442
 443         if (clone_flags & CLONE_NEWUSER) {
 444                 ret = create_user_ns(new);
 445                 if (ret < 0)
 446                         goto error_put;
 447         }
 448
 449 #ifdef CONFIG_KEYS
 450         /* new threads get their own thread keyrings if their parent already
 451          * had one */
 452         if (new->thread_keyring) {
 453                 key_put(new->thread_keyring);
 454                 new->thread_keyring = NULL;
 455                 if (clone_flags & CLONE_THREAD)
 456                         install_thread_keyring_to_cred(new);
 457         }
 458
 459         /* we share the process and session keyrings between all the threads in
 460          * a process - this is slightly icky as we violate COW credentials a
 461          * bit */
 462         if (!(clone_flags & CLONE_THREAD)) {
 463                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 464                 if (!tgcred) {
 465                         ret = -ENOMEM;
 466                         goto error_put;
 467                 }
 468                 atomic_set(&tgcred->usage, 1);
 469                 spin_lock_init(&tgcred->lock);
 470                 tgcred->process_keyring = NULL;
 471                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 472
 473                 release_tgcred(new);
 474                 new->tgcred = tgcred;
 475         }
 476 #endif
 477
 478         atomic_inc(&new->user->processes);
 479         p->cred = p->real_cred = get_cred(new);
 480         alter_cred_subscribers(new, 2);
 481         validate_creds(new);
 482         return 0;
 483
 484 error_put:
 485         put_cred(new);
 486         return ret;
 487 }
 488
 489 /**
 490  * commit_creds - Install new credentials upon the current task
 491  * @new: The credentials to be assigned
 492  *
 493  * Install a new set of credentials to the current task, using RCU to replace
 494  * the old set.  Both the objective and the subjective credentials pointers are
 495  * updated.  This function may not be called if the subjective credentials are
 496  * in an overridden state.
 497  *
 498  * This function eats the caller's reference to the new credentials.
 499  *
 500  * Always returns 0 thus allowing this function to be tail-called at the end
 501  * of, say, sys_setgid().
 502  */
 503 int commit_creds(struct cred *new)
 504 {
 505         struct task_struct *task = current;
 506         const struct cred *old = task->real_cred;
 507
 508         kdebug("commit_creds(%p{%d,%d})", new,
 509                atomic_read(&new->usage),
 510                read_cred_subscribers(new));
 511
 512         BUG_ON(task->cred != old);
 513 #ifdef CONFIG_DEBUG_CREDENTIALS
 514         BUG_ON(read_cred_subscribers(old) < 2);
 515         validate_creds(old);
 516         validate_creds(new);
 517 #endif
 518         BUG_ON(atomic_read(&new->usage) < 1);
 519
 520         security_commit_creds(new, old);
 521
 522         get_cred(new); /* we will require a ref for the subj creds too */
 523
 524         /* dumpability changes */
 525         if (old->euid != new->euid ||
 526             old->egid != new->egid ||
 527             old->fsuid != new->fsuid ||
 528             old->fsgid != new->fsgid ||
 529             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 530                 if (task->mm)
 531                         set_dumpable(task->mm, suid_dumpable);
 532                 task->pdeath_signal = 0;
 533                 smp_wmb();
 534         }
 535
 536         /* alter the thread keyring */
 537         if (new->fsuid != old->fsuid)
 538                 key_fsuid_changed(task);
 539         if (new->fsgid != old->fsgid)
 540                 key_fsgid_changed(task);
 541
 542         /* do it
 543          * - What if a process setreuid()'s and this brings the
 544          *   new uid over his NPROC rlimit?  We can check this now
 545          *   cheaply with the new uid cache, so if it matters
 546          *   we should be checking for it.  -DaveM
 547          */
 548         alter_cred_subscribers(new, 2);
 549         if (new->user != old->user)
 550                 atomic_inc(&new->user->processes);
 551         rcu_assign_pointer(task->real_cred, new);
 552         rcu_assign_pointer(task->cred, new);
 553         if (new->user != old->user)
 554                 atomic_dec(&old->user->processes);
 555         alter_cred_subscribers(old, -2);
 556
 557         sched_switch_user(task);
 558
 559         /* send notifications */
 560         if (new->uid   != old->uid  ||
 561             new->euid  != old->euid ||
 562             new->suid  != old->suid ||
 563             new->fsuid != old->fsuid)
 564                 proc_id_connector(task, PROC_EVENT_UID);
 565
 566         if (new->gid   != old->gid  ||
 567             new->egid  != old->egid ||
 568             new->sgid  != old->sgid ||
 569             new->fsgid != old->fsgid)
 570                 proc_id_connector(task, PROC_EVENT_GID);
 571
 572         /* release the old obj and subj refs both */
 573         put_cred(old);
 574         put_cred(old);
 575         return 0;
 576 }
 577 EXPORT_SYMBOL(commit_creds);
 578
 579 /**
 580  * abort_creds - Discard a set of credentials and unlock the current task
 581  * @new: The credentials that were going to be applied
 582  *
 583  * Discard a set of credentials that were under construction and unlock the
 584  * current task.
 585  */
 586 void abort_creds(struct cred *new)
 587 {
 588         kdebug("abort_creds(%p{%d,%d})", new,
 589                atomic_read(&new->usage),
 590                read_cred_subscribers(new));
 591
 592 #ifdef CONFIG_DEBUG_CREDENTIALS
 593         BUG_ON(read_cred_subscribers(new) != 0);
 594 #endif
 595         BUG_ON(atomic_read(&new->usage) < 1);
 596         put_cred(new);
 597 }
 598 EXPORT_SYMBOL(abort_creds);
 599
 600 /**
 601  * override_creds - Override the current process's subjective credentials
 602  * @new: The credentials to be assigned
 603  *
 604  * Install a set of temporary override subjective credentials on the current
 605  * process, returning the old set for later reversion.
 606  */
 607 const struct cred *override_creds(const struct cred *new)
 608 {
 609         const struct cred *old = current->cred;
 610
 611         kdebug("override_creds(%p{%d,%d})", new,
 612                atomic_read(&new->usage),
 613                read_cred_subscribers(new));
 614
 615         validate_creds(old);
 616         validate_creds(new);
 617         get_cred(new);
 618         alter_cred_subscribers(new, 1);
 619         rcu_assign_pointer(current->cred, new);
 620         alter_cred_subscribers(old, -1);
 621
 622         kdebug("override_creds() = %p{%d,%d}", old,
 623                atomic_read(&old->usage),
 624                read_cred_subscribers(old));
 625         return old;
 626 }
 627 EXPORT_SYMBOL(override_creds);
 628
 629 /**
 630  * revert_creds - Revert a temporary subjective credentials override
 631  * @old: The credentials to be restored
 632  *
 633  * Revert a temporary set of override subjective credentials to an old set,
 634  * discarding the override set.
 635  */
 636 void revert_creds(const struct cred *old)
 637 {
 638         const struct cred *override = current->cred;
 639
 640         kdebug("revert_creds(%p{%d,%d})", old,
 641                atomic_read(&old->usage),
 642                read_cred_subscribers(old));
 643
 644         validate_creds(old);
 645         validate_creds(override);
 646         alter_cred_subscribers(old, 1);
 647         rcu_assign_pointer(current->cred, old);
 648         alter_cred_subscribers(override, -1);
 649         put_cred(override);
 650 }
 651 EXPORT_SYMBOL(revert_creds);
 652
 653 /*
 654  * initialise the credentials stuff
 655  */
 656 void __init cred_init(void)
 657 {
 658         /* allocate a slab in which we can store credentials */
 659         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 660                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 661 }
 662
 663 /**
 664  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 665  * @daemon: A userspace daemon to be used as a reference
 666  *
 667  * Prepare a set of credentials for a kernel service.  This can then be used to
 668  * override a task's own credentials so that work can be done on behalf of that
 669  * task that requires a different subjective context.
 670  *
 671  * @daemon is used to provide a base for the security record, but can be NULL.
 672  * If @daemon is supplied, then the security data will be derived from that;
 673  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 674  *
 675  * The caller may change these controls afterwards if desired.
 676  *
 677  * Returns the new credentials or NULL if out of memory.
 678  *
 679  * Does not take, and does not return holding current->cred_replace_mutex.
 680  */
 681 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 682 {
 683         const struct cred *old;
 684         struct cred *new;
 685
 686         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 687         if (!new)
 688                 return NULL;
 689
 690         kdebug("prepare_kernel_cred() alloc %p", new);
 691
 692         if (daemon)
 693                 old = get_task_cred(daemon);
 694         else
 695                 old = get_cred(&init_cred);
 696
 697         validate_creds(old);
 698
 699         *new = *old;
 700         get_uid(new->user);
 701         get_group_info(new->group_info);
 702
 703 #ifdef CONFIG_KEYS
 704         atomic_inc(&init_tgcred.usage);
 705         new->tgcred = &init_tgcred;
 706         new->request_key_auth = NULL;
 707         new->thread_keyring = NULL;
 708         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 709 #endif
 710
 711 #ifdef CONFIG_SECURITY
 712         new->security = NULL;
 713 #endif
 714         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 715                 goto error;
 716
 717         atomic_set(&new->usage, 1);
 718         set_cred_subscribers(new, 0);
 719         put_cred(old);
 720         validate_creds(new);
 721         return new;
 722
 723 error:
 724         put_cred(new);
 725         put_cred(old);
 726         return NULL;
 727 }
 728 EXPORT_SYMBOL(prepare_kernel_cred);
 729
 730 /**
 731  * set_security_override - Set the security ID in a set of credentials
 732  * @new: The credentials to alter
 733  * @secid: The LSM security ID to set
 734  *
 735  * Set the LSM security ID in a set of credentials so that the subjective
 736  * security is overridden when an alternative set of credentials is used.
 737  */
 738 int set_security_override(struct cred *new, u32 secid)
 739 {
 740         return security_kernel_act_as(new, secid);
 741 }
 742 EXPORT_SYMBOL(set_security_override);
 743
 744 /**
 745  * set_security_override_from_ctx - Set the security ID in a set of credentials
 746  * @new: The credentials to alter
 747  * @secctx: The LSM security context to generate the security ID from.
 748  *
 749  * Set the LSM security ID in a set of credentials so that the subjective
 750  * security is overridden when an alternative set of credentials is used.  The
 751  * security ID is specified in string form as a security context to be
 752  * interpreted by the LSM.
 753  */
 754 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 755 {
 756         u32 secid;
 757         int ret;
 758
 759         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 760         if (ret < 0)
 761                 return ret;
 762
 763         return set_security_override(new, secid);
 764 }
 765 EXPORT_SYMBOL(set_security_override_from_ctx);
 766
 767 /**
 768  * set_create_files_as - Set the LSM file create context in a set of credentials
 769  * @new: The credentials to alter
 770  * @inode: The inode to take the context from
 771  *
 772  * Change the LSM file creation context in a set of credentials to be the same
 773  * as the object context of the specified inode, so that the new inodes have
 774  * the same MAC context as that inode.
 775  */
 776 int set_create_files_as(struct cred *new, struct inode *inode)
 777 {
 778         new->fsuid = inode->i_uid;
 779         new->fsgid = inode->i_gid;
 780         return security_kernel_create_files_as(new, inode);
 781 }
 782 EXPORT_SYMBOL(set_create_files_as);
 783
 784 #ifdef CONFIG_DEBUG_CREDENTIALS
 785
 786 bool creds_are_invalid(const struct cred *cred)
 787 {
 788         if (cred->magic != CRED_MAGIC)
 789                 return true;
 790         if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
 791                 return true;
 792 #ifdef CONFIG_SECURITY_SELINUX
 793         if (selinux_is_enabled()) {
 794                 if ((unsigned long) cred->security < PAGE_SIZE)
 795                         return true;
 796                 if ((*(u32 *)cred->security & 0xffffff00) ==
 797                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 798                         return true;
 799         }
 800 #endif
 801         return false;
 802 }
 803 EXPORT_SYMBOL(creds_are_invalid);
 804
 805 /*
 806  * dump invalid credentials
 807  */
 808 static void dump_invalid_creds(const struct cred *cred, const char *label,
 809                                const struct task_struct *tsk)
 810 {
 811         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 812                label, cred,
 813                cred == &init_cred ? "[init]" : "",
 814                cred == tsk->real_cred ? "[real]" : "",
 815                cred == tsk->cred ? "[eff]" : "");
 816         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 817                cred->magic, cred->put_addr);
 818         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 819                atomic_read(&cred->usage),
 820                read_cred_subscribers(cred));
 821         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 822                cred->uid, cred->euid, cred->suid, cred->fsuid);
 823         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 824                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 825 #ifdef CONFIG_SECURITY
 826         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 827         if ((unsigned long) cred->security >= PAGE_SIZE &&
 828             (((unsigned long) cred->security & 0xffffff00) !=
 829              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 830                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 831                        ((u32*)cred->security)[0],
 832                        ((u32*)cred->security)[1]);
 833 #endif
 834 }
 835
 836 /*
 837  * report use of invalid credentials
 838  */
 839 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 840 {
 841         printk(KERN_ERR "CRED: Invalid credentials\n");
 842         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 843         dump_invalid_creds(cred, "Specified", current);
 844         BUG();
 845 }
 846 EXPORT_SYMBOL(__invalid_creds);
 847
 848 /*
 849  * check the credentials on a process
 850  */
 851 void __validate_process_creds(struct task_struct *tsk,
 852                               const char *file, unsigned line)
 853 {
 854         if (tsk->cred == tsk->real_cred) {
 855                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 856                              creds_are_invalid(tsk->cred)))
 857                         goto invalid_creds;
 858         } else {
 859                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 860                              read_cred_subscribers(tsk->cred) < 1 ||
 861                              creds_are_invalid(tsk->real_cred) ||
 862                              creds_are_invalid(tsk->cred)))
 863                         goto invalid_creds;
 864         }
 865         return;
 866
 867 invalid_creds:
 868         printk(KERN_ERR "CRED: Invalid process credentials\n");
 869         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 870
 871         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 872         if (tsk->cred != tsk->real_cred)
 873                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 874         else
 875                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 876         BUG();
 877 }
 878 EXPORT_SYMBOL(__validate_process_creds);
 879
 880 /*
 881  * check creds for do_exit()
 882  */
 883 void validate_creds_for_do_exit(struct task_struct *tsk)
 884 {
 885         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 886                tsk->real_cred, tsk->cred,
 887                atomic_read(&tsk->cred->usage),
 888                read_cred_subscribers(tsk->cred));
 889
 890         __validate_process_creds(tsk, __FILE__, __LINE__);
 891 }
 892
 893 #endif /* CONFIG_DEBUG_CREDENTIALS */